DNA Helps Researchers Trace Origins of Domestic Chicken

Durham University researchers have used ancient DNA to study how a jungle bird transformed into the domestic chicken.

According to the researchers, chickens that lived 2000 to 3000 years ago looked quite different from today's barnyard chickens.

The study shows that chickens have accumulated certain traits recently. A common trait, such as the yellow skin color, for example, evolved just 500 years ago.

"It's a blink of an eye from an evolutionary perspective," said co-author Greger Larson at Durham University in the United Kingdom.

Chickens have originated from a bird called Red Junglefowl, which was domesticated by humans some 4,000-5,000 years ago in South Asia. The current study is part of a larger study that is looking into the genetic changes that occurred with domestication of wild plants, birds and animals.

For the study, the team analyzed chicken bones obtained from 81 sites across Europe. The bones were 200 to 2,300 years old.

Researchers concentrated on studying two genes; called BCDO2 and TSHR. BCDO2 codes for the yellow coloring of the chicken while TSHR is associated with thyroid production.

Why domestic chickens have genes for thyroid production is unknown. One theory is that the hormone production helps them lay eggs throughout the year. Their wild counterparts lay eggs seasonally.

The study showed that BCDO2 and TSHR were uncommon in ancient chicken DNA, suggesting that these birds looked quite different in ancient times.

"Just because a plant or animal trait is common today doesn't mean that it was bred into them from the beginning," Larson said. "It demonstrates that the pets and livestock we know today -- dogs, chickens, horses, cows -- are probably radically different from the ones our great-great-grandparents knew."

"...They are subjected to the whim of human fancy and control, [so] radical change in the way they look can be achieved in very few generations," he added, according to a news release.

The study,"Establishing the validity of domestication genes using DNA from ancient chickens," is published in the journal Proceedings of the National Academy of Sciences.

Chicken bones also help archaeologists decode human movement. A recent study from the University of Adelaide had made use of chicken bone DNA to declare that Europeans were the first people to reach North America.